Pocket knives provide a convenient tool for cutting that may be easily carried by a user for deployment when desired. For some pocket knife designs, two hands are needed to deploy and retract a blade, while other designs include a spring that assists a user to deploy or retract the blade using a single hand. Each design balances the convenience and speed of operation with increased risk associated with inadvertent operation.
A switchblade is a particular style of pocket knife that has a folding or sliding blade that automatically deploys when an actuator is operated. A single action switchblade typically includes a spring under tension with the blade when retracted, and operation of the actuator releases the blade to allow the spring tension to automatically deploy the blade. Once deployed, the actuator is released to hold the blade in the deployed position. To retract a single action switchblade, the actuator is again operated to release the blade, and the blade must be manually retracted against the spring tension. For example, a single action switchblade design may include a charging handle that may be manually operated to retract the blade against the spring tension. In contrast, a double action switchblade typically includes a slider engaged with the actuator, front and rear operators connected by a spring to alternately engage with the blade and slider, and front and rear locks engaged with the blade in the deployed and retracted positions, respectively. To deploy a double action switchblade, the actuator is moved forward to move the slider forward. Forward movement of the slider moves the front operator forward while the rear operator is engaged with the rear of the blade to charge the spring. Forward movement of the slider eventually releases the rear lock to allow the charged spring to deploy the blade, and the front lock engages with the deployed blade to lock the blade in the deployed position. To retract a double action switchblade, the actuator is moved rearward to move the slider rearward. Rearward movement of the slider moves the rear operator rearward while the front operator is engaged with the blade to charge the spring. Rearward movement of the slider eventually releases the front lock to allow the charged spring to retract the blade, and the rear lock engages with the retracted blade to lock the blade in the retracted position.
Although a double action switchblade provides convenient one-handed operation, the slider that provides this convenient functionality generally requires precise manufacturing tolerances to achieve the required clearances inside the switchblade while ensuring years of reliable operation. The precise manufacturing tolerances increase the cost of the switchblade, as well as the cost of replacement parts and repairs. In addition, the conventional arrangement of the slider, front and rear operators, spring, and front and rear locks inside the switchblade increases the size of the switchblade to ensure adequate clearance between the components as they move. Therefore, the need exists for an improved switchblade that does not require a precisely machined slider and that can provide the desired functionality in a smaller casing.